Syngas generated by the gasification of coal or biomass has many potential applications, including the production of hydrocarbon transportation fuels, chemicals (including hydrogen), and electric power. Most syngases contain impurities that may make it unsuitable for various end uses. Sulfur-containing molecules, primarily H2S and COS, are especially troublesome catalyst poisons that must be removed to the parts per billion levels for the production of fuels and chemicals. Although technical approaches exist for removal of these sulfur species, these approaches typically tend to be rather costly, require temperature fluctuations, and in many cases backup sacrificial adsorbents. Since catalytic processes for the production of fuels and chemicals typically operate in the range of 225-300° C., a process that requires the cooling of syngas followed by a re-heating is energy inefficient. A process that is capable of removing sulfur gases to the 50 ppb level at or somewhat above the temperature of the synthesis step is much preferred.
Syngas composition is a function of several parameters, including gasifier type, operating conditions and fuel source. In the case of coal, a combination of zinc oxide with a regenerable downstream polishing bed is a promising approach. For biomass, which typically generates less than 100 ppm of sulfur gases, a stand-alone regenerable sulfur sorbent may provide an attractive approach. In the past, the development of regenerable metal sorbents has typically been stymied by the strong tendency of the metals to sinter or aggregate during the regeneration process. This results in a loss of surface area and therefore sulfur adsorbent capacity. What is needed, therefore, is a method, system and device that allows for deep (ppb) desulfurization of fuel gasses. What is also needed is a regenerable desulfurization system. What is also needed is a desulfurization system that performs effective desulfurization at warm temperatures. The present invention provides a solution to these needs.
Additional advantages and novel features of the present invention will be set forth as follows and will be readily apparent from the descriptions and demonstrations set forth herein. Accordingly, the following descriptions of the present invention should be seen as illustrative of the invention and not as limiting in any way.